Fair son worked to the degree (2,2,3)
I believe the answer is:
in so far
'to the degree' is the definition.
('in so far as' can mean 'to the degree that')
'fair son worked' is the wordplay.
'worked' is an anagram indicator.
'fair'+'son'='fairson'
'fairson' with letters rearranged gives 'IN SO FAR'.
(Other definitions for in so far that I've seen before include "Inasmuch" , "To the degree or extent that" .)